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/*
 * Copyright (c) 2011-2012, Stephen Colebourne & Michael Nascimento Santos
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 *  * Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 *  * Neither the name of JSR-310 nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package java.time.temporal;

import static java.time.DayOfWeek.THURSDAY;
import static java.time.DayOfWeek.WEDNESDAY;
import static java.time.temporal.ChronoField.DAY_OF_WEEK;
import static java.time.temporal.ChronoField.DAY_OF_YEAR;
import static java.time.temporal.ChronoField.EPOCH_DAY;
import static java.time.temporal.ChronoField.MONTH_OF_YEAR;
import static java.time.temporal.ChronoField.YEAR;
import static java.time.temporal.ChronoUnit.DAYS;
import static java.time.temporal.ChronoUnit.FOREVER;
import static java.time.temporal.ChronoUnit.MONTHS;
import static java.time.temporal.ChronoUnit.WEEKS;
import static java.time.temporal.ChronoUnit.YEARS;

import java.time.DateTimeException;
import java.time.Duration;
import java.time.LocalDate;
import java.time.chrono.ChronoLocalDate;
import java.time.chrono.Chronology;
import java.time.chrono.IsoChronology;
import java.time.format.ResolverStyle;
import java.util.Locale;
import java.util.Map;
import java.util.Objects;
import java.util.ResourceBundle;

import sun.util.locale.provider.LocaleProviderAdapter;
import sun.util.locale.provider.LocaleResources;

/**
 * Fields and units specific to the ISO-8601 calendar system,
 * including quarter-of-year and week-based-year.
 * <p>
 * This class defines fields and units that are specific to the ISO calendar system.
 *
 * <h3>Quarter of year</h3>
 * The ISO-8601 standard is based on the standard civic 12 month year.
 * This is commonly divided into four quarters, often abbreviated as Q1, Q2, Q3 and Q4.
 * <p>
 * January, February and March are in Q1.
 * April, May and June are in Q2.
 * July, August and September are in Q3.
 * October, November and December are in Q4.
 * <p>
 * The complete date is expressed using three fields:
 * <ul>
 * <li>{@link #DAY_OF_QUARTER DAY_OF_QUARTER} - the day within the quarter, from 1 to 90, 91 or 92
 * <li>{@link #QUARTER_OF_YEAR QUARTER_OF_YEAR} - the week within the week-based-year
 * <li>{@link ChronoField#YEAR YEAR} - the standard ISO year
 * </ul>
 *
 * <h3>Week based years</h3>
 * The ISO-8601 standard was originally intended as a data interchange format,
 * defining a string format for dates and times. However, it also defines an
 * alternate way of expressing the date, based on the concept of week-based-year.
 * <p>
 * The date is expressed using three fields:
 * <ul>
 * <li>{@link ChronoField#DAY_OF_WEEK DAY_OF_WEEK} - the standard field defining the
 * day-of-week from Monday (1) to Sunday (7)
 * <li>{@link #WEEK_OF_WEEK_BASED_YEAR} - the week within the week-based-year
 * <li>{@link #WEEK_BASED_YEAR WEEK_BASED_YEAR} - the week-based-year
 * </ul>
 * The week-based-year itself is defined relative to the standard ISO proleptic year.
 * It differs from the standard year in that it always starts on a Monday.
 * <p>
 * The first week of a week-based-year is the first Monday-based week of the standard
 * ISO year that has at least 4 days in the new year.
 * <ul>
 * <li>If January 1st is Monday then week 1 starts on January 1st
 * <li>If January 1st is Tuesday then week 1 starts on December 31st of the previous standard year
 * <li>If January 1st is Wednesday then week 1 starts on December 30th of the previous standard year
 * <li>If January 1st is Thursday then week 1 starts on December 29th of the previous standard year
 * <li>If January 1st is Friday then week 1 starts on January 4th
 * <li>If January 1st is Saturday then week 1 starts on January 3rd
 * <li>If January 1st is Sunday then week 1 starts on January 2nd
 * </ul>
 * There are 52 weeks in most week-based years, however on occasion there are 53 weeks.
 * <p>
 * For example:
 *
 * <table cellpadding="0" cellspacing="3" border="0" style="text-align: left; width: 50%;">
 * <caption>Examples of Week based Years</caption>
 * <tr><th>Date</th><th>Day-of-week</th><th>Field values</th></tr>
 * <tr><th>2008-12-28</th><td>Sunday</td><td>Week 52 of week-based-year 2008</td></tr>
 * <tr><th>2008-12-29</th><td>Monday</td><td>Week 1 of week-based-year 2009</td></tr>
 * <tr><th>2008-12-31</th><td>Wednesday</td><td>Week 1 of week-based-year 2009</td></tr>
 * <tr><th>2009-01-01</th><td>Thursday</td><td>Week 1 of week-based-year 2009</td></tr>
 * <tr><th>2009-01-04</th><td>Sunday</td><td>Week 1 of week-based-year 2009</td></tr>
 * <tr><th>2009-01-05</th><td>Monday</td><td>Week 2 of week-based-year 2009</td></tr>
 * </table>
 *
 * @implSpec <p> This class is immutable and thread-safe.
 * @since 1.8
 */
public final class IsoFields {

  /**
   * The field that represents the day-of-quarter.
   * <p>
   * This field allows the day-of-quarter value to be queried and set.
   * The day-of-quarter has values from 1 to 90 in Q1 of a standard year, from 1 to 91
   * in Q1 of a leap year, from 1 to 91 in Q2 and from 1 to 92 in Q3 and Q4.
   * <p>
   * The day-of-quarter can only be calculated if the day-of-year, month-of-year and year
   * are available.
   * <p>
   * When setting this field, the value is allowed to be partially lenient, taking any
   * value from 1 to 92. If the quarter has less than 92 days, then day 92, and
   * potentially day 91, is in the following quarter.
   * <p>
   * In the resolving phase of parsing, a date can be created from a year,
   * quarter-of-year and day-of-quarter.
   * <p>
   * In {@linkplain ResolverStyle#STRICT strict mode}, all three fields are
   * validated against their range of valid values. The day-of-quarter field
   * is validated from 1 to 90, 91 or 92 depending on the year and quarter.
   * <p>
   * In {@linkplain ResolverStyle#SMART smart mode}, all three fields are
   * validated against their range of valid values. The day-of-quarter field is
   * validated between 1 and 92, ignoring the actual range based on the year and quarter.
   * If the day-of-quarter exceeds the actual range by one day, then the resulting date
   * is one day later. If the day-of-quarter exceeds the actual range by two days,
   * then the resulting date is two days later.
   * <p>
   * In {@linkplain ResolverStyle#LENIENT lenient mode}, only the year is validated
   * against the range of valid values. The resulting date is calculated equivalent to
   * the following three stage approach. First, create a date on the first of January
   * in the requested year. Then take the quarter-of-year, subtract one, and add the
   * amount in quarters to the date. Finally, take the day-of-quarter, subtract one,
   * and add the amount in days to the date.
   * <p>
   * This unit is an immutable and thread-safe singleton.
   */
  public static final TemporalField DAY_OF_QUARTER = Field.DAY_OF_QUARTER;
  /**
   * The field that represents the quarter-of-year.
   * <p>
   * This field allows the quarter-of-year value to be queried and set.
   * The quarter-of-year has values from 1 to 4.
   * <p>
   * The quarter-of-year can only be calculated if the month-of-year is available.
   * <p>
   * In the resolving phase of parsing, a date can be created from a year,
   * quarter-of-year and day-of-quarter.
   * See {@link #DAY_OF_QUARTER} for details.
   * <p>
   * This unit is an immutable and thread-safe singleton.
   */
  public static final TemporalField QUARTER_OF_YEAR = Field.QUARTER_OF_YEAR;
  /**
   * The field that represents the week-of-week-based-year.
   * <p>
   * This field allows the week of the week-based-year value to be queried and set.
   * The week-of-week-based-year has values from 1 to 52, or 53 if the
   * week-based-year has 53 weeks.
   * <p>
   * In the resolving phase of parsing, a date can be created from a
   * week-based-year, week-of-week-based-year and day-of-week.
   * <p>
   * In {@linkplain ResolverStyle#STRICT strict mode}, all three fields are
   * validated against their range of valid values. The week-of-week-based-year
   * field is validated from 1 to 52 or 53 depending on the week-based-year.
   * <p>
   * In {@linkplain ResolverStyle#SMART smart mode}, all three fields are
   * validated against their range of valid values. The week-of-week-based-year
   * field is validated between 1 and 53, ignoring the week-based-year.
   * If the week-of-week-based-year is 53, but the week-based-year only has
   * 52 weeks, then the resulting date is in week 1 of the following week-based-year.
   * <p>
   * In {@linkplain ResolverStyle#LENIENT lenient mode}, only the week-based-year
   * is validated against the range of valid values. If the day-of-week is outside
   * the range 1 to 7, then the resulting date is adjusted by a suitable number of
   * weeks to reduce the day-of-week to the range 1 to 7. If the week-of-week-based-year
   * value is outside the range 1 to 52, then any excess weeks are added or subtracted
   * from the resulting date.
   * <p>
   * This unit is an immutable and thread-safe singleton.
   */
  public static final TemporalField WEEK_OF_WEEK_BASED_YEAR = Field.WEEK_OF_WEEK_BASED_YEAR;
  /**
   * The field that represents the week-based-year.
   * <p>
   * This field allows the week-based-year value to be queried and set.
   * <p>
   * The field has a range that matches {@link LocalDate#MAX} and {@link LocalDate#MIN}.
   * <p>
   * In the resolving phase of parsing, a date can be created from a
   * week-based-year, week-of-week-based-year and day-of-week.
   * See {@link #WEEK_OF_WEEK_BASED_YEAR} for details.
   * <p>
   * This unit is an immutable and thread-safe singleton.
   */
  public static final TemporalField WEEK_BASED_YEAR = Field.WEEK_BASED_YEAR;
  /**
   * The unit that represents week-based-years for the purpose of addition and subtraction.
   * <p>
   * This allows a number of week-based-years to be added to, or subtracted from, a date.
   * The unit is equal to either 52 or 53 weeks.
   * The estimated duration of a week-based-year is the same as that of a standard ISO
   * year at {@code 365.2425 Days}.
   * <p>
   * The rules for addition add the number of week-based-years to the existing value
   * for the week-based-year field. If the resulting week-based-year only has 52 weeks,
   * then the date will be in week 1 of the following week-based-year.
   * <p>
   * This unit is an immutable and thread-safe singleton.
   */
  public static final TemporalUnit WEEK_BASED_YEARS = Unit.WEEK_BASED_YEARS;
  /**
   * Unit that represents the concept of a quarter-year.
   * For the ISO calendar system, it is equal to 3 months.
   * The estimated duration of a quarter-year is one quarter of {@code 365.2425 Days}.
   * <p>
   * This unit is an immutable and thread-safe singleton.
   */
  public static final TemporalUnit QUARTER_YEARS = Unit.QUARTER_YEARS;

  /**
   * Restricted constructor.
   */
  private IsoFields() {
    throw new AssertionError("Not instantiable");
  }

  //-----------------------------------------------------------------------

  /**
   * Implementation of the field.
   */
  private static enum Field implements TemporalField {
    DAY_OF_QUARTER {
      @Override
      public TemporalUnit getBaseUnit() {
        return DAYS;
      }

      @Override
      public TemporalUnit getRangeUnit() {
        return QUARTER_YEARS;
      }

      @Override
      public ValueRange range() {
        return ValueRange.of(1, 90, 92);
      }

      @Override
      public boolean isSupportedBy(TemporalAccessor temporal) {
        return temporal.isSupported(DAY_OF_YEAR) && temporal.isSupported(MONTH_OF_YEAR) &&
            temporal.isSupported(YEAR) && isIso(temporal);
      }

      @Override
      public ValueRange rangeRefinedBy(TemporalAccessor temporal) {
        if (isSupportedBy(temporal) == false) {
          throw new UnsupportedTemporalTypeException("Unsupported field: DayOfQuarter");
        }
        long qoy = temporal.getLong(QUARTER_OF_YEAR);
        if (qoy == 1) {
          long year = temporal.getLong(YEAR);
          return (IsoChronology.INSTANCE.isLeapYear(year) ? ValueRange.of(1, 91)
              : ValueRange.of(1, 90));
        } else if (qoy == 2) {
          return ValueRange.of(1, 91);
        } else if (qoy == 3 || qoy == 4) {
          return ValueRange.of(1, 92);
        } // else value not from 1 to 4, so drop through
        return range();
      }

      @Override
      public long getFrom(TemporalAccessor temporal) {
        if (isSupportedBy(temporal) == false) {
          throw new UnsupportedTemporalTypeException("Unsupported field: DayOfQuarter");
        }
        int doy = temporal.get(DAY_OF_YEAR);
        int moy = temporal.get(MONTH_OF_YEAR);
        long year = temporal.getLong(YEAR);
        return doy - QUARTER_DAYS[((moy - 1) / 3) + (IsoChronology.INSTANCE.isLeapYear(year) ? 4
            : 0)];
      }

      @SuppressWarnings("unchecked")
      @Override
      public <R extends Temporal> R adjustInto(R temporal, long newValue) {
        // calls getFrom() to check if supported
        long curValue = getFrom(temporal);
        range().checkValidValue(newValue, this);  // leniently check from 1 to 92 TODO: check
        return (R) temporal
            .with(DAY_OF_YEAR, temporal.getLong(DAY_OF_YEAR) + (newValue - curValue));
      }

      @Override
      public ChronoLocalDate resolve(
          Map<TemporalField, Long> fieldValues, TemporalAccessor partialTemporal,
          ResolverStyle resolverStyle) {
        Long yearLong = fieldValues.get(YEAR);
        Long qoyLong = fieldValues.get(QUARTER_OF_YEAR);
        if (yearLong == null || qoyLong == null) {
          return null;
        }
        int y = YEAR.checkValidIntValue(yearLong);  // always validate
        long doq = fieldValues.get(DAY_OF_QUARTER);
        ensureIso(partialTemporal);
        LocalDate date;
        if (resolverStyle == ResolverStyle.LENIENT) {
          date = LocalDate.of(y, 1, 1)
              .plusMonths(Math.multiplyExact(Math.subtractExact(qoyLong, 1), 3));
          doq = Math.subtractExact(doq, 1);
        } else {
          int qoy = QUARTER_OF_YEAR.range()
              .checkValidIntValue(qoyLong, QUARTER_OF_YEAR);  // validated
          date = LocalDate.of(y, ((qoy - 1) * 3) + 1, 1);
          if (doq < 1 || doq > 90) {
            if (resolverStyle == ResolverStyle.STRICT) {
              rangeRefinedBy(date).checkValidValue(doq, this);  // only allow exact range
            } else {  // SMART
              range().checkValidValue(doq, this);  // allow 1-92 rolling into next quarter
            }
          }
          doq--;
        }
        fieldValues.remove(this);
        fieldValues.remove(YEAR);
        fieldValues.remove(QUARTER_OF_YEAR);
        return date.plusDays(doq);
      }

      @Override
      public String toString() {
        return "DayOfQuarter";
      }
    },
    QUARTER_OF_YEAR {
      @Override
      public TemporalUnit getBaseUnit() {
        return QUARTER_YEARS;
      }

      @Override
      public TemporalUnit getRangeUnit() {
        return YEARS;
      }

      @Override
      public ValueRange range() {
        return ValueRange.of(1, 4);
      }

      @Override
      public boolean isSupportedBy(TemporalAccessor temporal) {
        return temporal.isSupported(MONTH_OF_YEAR) && isIso(temporal);
      }

      @Override
      public long getFrom(TemporalAccessor temporal) {
        if (isSupportedBy(temporal) == false) {
          throw new UnsupportedTemporalTypeException("Unsupported field: QuarterOfYear");
        }
        long moy = temporal.getLong(MONTH_OF_YEAR);
        return ((moy + 2) / 3);
      }

      @SuppressWarnings("unchecked")
      @Override
      public <R extends Temporal> R adjustInto(R temporal, long newValue) {
        // calls getFrom() to check if supported
        long curValue = getFrom(temporal);
        range().checkValidValue(newValue, this);  // strictly check from 1 to 4
        return (R) temporal
            .with(MONTH_OF_YEAR, temporal.getLong(MONTH_OF_YEAR) + (newValue - curValue) * 3);
      }

      @Override
      public String toString() {
        return "QuarterOfYear";
      }
    },
    WEEK_OF_WEEK_BASED_YEAR {
      @Override
      public String getDisplayName(Locale locale) {
        Objects.requireNonNull(locale, "locale");
        LocaleResources lr = LocaleProviderAdapter.getResourceBundleBased()
            .getLocaleResources(locale);
        ResourceBundle rb = lr.getJavaTimeFormatData();
        return rb.containsKey("field.week") ? rb.getString("field.week") : toString();
      }

      @Override
      public TemporalUnit getBaseUnit() {
        return WEEKS;
      }

      @Override
      public TemporalUnit getRangeUnit() {
        return WEEK_BASED_YEARS;
      }

      @Override
      public ValueRange range() {
        return ValueRange.of(1, 52, 53);
      }

      @Override
      public boolean isSupportedBy(TemporalAccessor temporal) {
        return temporal.isSupported(EPOCH_DAY) && isIso(temporal);
      }

      @Override
      public ValueRange rangeRefinedBy(TemporalAccessor temporal) {
        if (isSupportedBy(temporal) == false) {
          throw new UnsupportedTemporalTypeException("Unsupported field: WeekOfWeekBasedYear");
        }
        return getWeekRange(LocalDate.from(temporal));
      }

      @Override
      public long getFrom(TemporalAccessor temporal) {
        if (isSupportedBy(temporal) == false) {
          throw new UnsupportedTemporalTypeException("Unsupported field: WeekOfWeekBasedYear");
        }
        return getWeek(LocalDate.from(temporal));
      }

      @SuppressWarnings("unchecked")
      @Override
      public <R extends Temporal> R adjustInto(R temporal, long newValue) {
        // calls getFrom() to check if supported
        range().checkValidValue(newValue, this);  // lenient range
        return (R) temporal.plus(Math.subtractExact(newValue, getFrom(temporal)), WEEKS);
      }

      @Override
      public ChronoLocalDate resolve(
          Map<TemporalField, Long> fieldValues, TemporalAccessor partialTemporal,
          ResolverStyle resolverStyle) {
        Long wbyLong = fieldValues.get(WEEK_BASED_YEAR);
        Long dowLong = fieldValues.get(DAY_OF_WEEK);
        if (wbyLong == null || dowLong == null) {
          return null;
        }
        int wby = WEEK_BASED_YEAR.range()
            .checkValidIntValue(wbyLong, WEEK_BASED_YEAR);  // always validate
        long wowby = fieldValues.get(WEEK_OF_WEEK_BASED_YEAR);
        ensureIso(partialTemporal);
        LocalDate date = LocalDate.of(wby, 1, 4);
        if (resolverStyle == ResolverStyle.LENIENT) {
          long dow = dowLong;  // unvalidated
          if (dow > 7) {
            date = date.plusWeeks((dow - 1) / 7);
            dow = ((dow - 1) % 7) + 1;
          } else if (dow < 1) {
            date = date.plusWeeks(Math.subtractExact(dow, 7) / 7);
            dow = ((dow + 6) % 7) + 1;
          }
          date = date.plusWeeks(Math.subtractExact(wowby, 1)).with(DAY_OF_WEEK, dow);
        } else {
          int dow = DAY_OF_WEEK.checkValidIntValue(dowLong);  // validated
          if (wowby < 1 || wowby > 52) {
            if (resolverStyle == ResolverStyle.STRICT) {
              getWeekRange(date).checkValidValue(wowby, this);  // only allow exact range
            } else {  // SMART
              range().checkValidValue(wowby, this);  // allow 1-53 rolling into next year
            }
          }
          date = date.plusWeeks(wowby - 1).with(DAY_OF_WEEK, dow);
        }
        fieldValues.remove(this);
        fieldValues.remove(WEEK_BASED_YEAR);
        fieldValues.remove(DAY_OF_WEEK);
        return date;
      }

      @Override
      public String toString() {
        return "WeekOfWeekBasedYear";
      }
    },
    WEEK_BASED_YEAR {
      @Override
      public TemporalUnit getBaseUnit() {
        return WEEK_BASED_YEARS;
      }

      @Override
      public TemporalUnit getRangeUnit() {
        return FOREVER;
      }

      @Override
      public ValueRange range() {
        return YEAR.range();
      }

      @Override
      public boolean isSupportedBy(TemporalAccessor temporal) {
        return temporal.isSupported(EPOCH_DAY) && isIso(temporal);
      }

      @Override
      public long getFrom(TemporalAccessor temporal) {
        if (isSupportedBy(temporal) == false) {
          throw new UnsupportedTemporalTypeException("Unsupported field: WeekBasedYear");
        }
        return getWeekBasedYear(LocalDate.from(temporal));
      }

      @SuppressWarnings("unchecked")
      @Override
      public <R extends Temporal> R adjustInto(R temporal, long newValue) {
        if (isSupportedBy(temporal) == false) {
          throw new UnsupportedTemporalTypeException("Unsupported field: WeekBasedYear");
        }
        int newWby = range().checkValidIntValue(newValue, WEEK_BASED_YEAR);  // strict check
        LocalDate date = LocalDate.from(temporal);
        int dow = date.get(DAY_OF_WEEK);
        int week = getWeek(date);
        if (week == 53 && getWeekRange(newWby) == 52) {
          week = 52;
        }
        LocalDate resolved = LocalDate.of(newWby, 1, 4);  // 4th is guaranteed to be in week one
        int days = (dow - resolved.get(DAY_OF_WEEK)) + ((week - 1) * 7);
        resolved = resolved.plusDays(days);
        return (R) temporal.with(resolved);
      }

      @Override
      public String toString() {
        return "WeekBasedYear";
      }
    };

    @Override
    public boolean isDateBased() {
      return true;
    }

    @Override
    public boolean isTimeBased() {
      return false;
    }

    @Override
    public ValueRange rangeRefinedBy(TemporalAccessor temporal) {
      return range();
    }

    //-------------------------------------------------------------------------
    private static final int[] QUARTER_DAYS = {0, 90, 181, 273, 0, 91, 182, 274};

    private static boolean isIso(TemporalAccessor temporal) {
      return Chronology.from(temporal).equals(IsoChronology.INSTANCE);
    }

    private static void ensureIso(TemporalAccessor temporal) {
      if (isIso(temporal) == false) {
        throw new DateTimeException("Resolve requires IsoChronology");
      }
    }

    private static ValueRange getWeekRange(LocalDate date) {
      int wby = getWeekBasedYear(date);
      return ValueRange.of(1, getWeekRange(wby));
    }

    private static int getWeekRange(int wby) {
      LocalDate date = LocalDate.of(wby, 1, 1);
      // 53 weeks if standard year starts on Thursday, or Wed in a leap year
      if (date.getDayOfWeek() == THURSDAY || (date.getDayOfWeek() == WEDNESDAY && date
          .isLeapYear())) {
        return 53;
      }
      return 52;
    }

    private static int getWeek(LocalDate date) {
      int dow0 = date.getDayOfWeek().ordinal();
      int doy0 = date.getDayOfYear() - 1;
      int doyThu0 =
          doy0 + (3 - dow0);  // adjust to mid-week Thursday (which is 3 indexed from zero)
      int alignedWeek = doyThu0 / 7;
      int firstThuDoy0 = doyThu0 - (alignedWeek * 7);
      int firstMonDoy0 = firstThuDoy0 - 3;
      if (firstMonDoy0 < -3) {
        firstMonDoy0 += 7;
      }
      if (doy0 < firstMonDoy0) {
        return (int) getWeekRange(date.withDayOfYear(180).minusYears(1)).getMaximum();
      }
      int week = ((doy0 - firstMonDoy0) / 7) + 1;
      if (week == 53) {
        if ((firstMonDoy0 == -3 || (firstMonDoy0 == -2 && date.isLeapYear())) == false) {
          week = 1;
        }
      }
      return week;
    }

    private static int getWeekBasedYear(LocalDate date) {
      int year = date.getYear();
      int doy = date.getDayOfYear();
      if (doy <= 3) {
        int dow = date.getDayOfWeek().ordinal();
        if (doy - dow < -2) {
          year--;
        }
      } else if (doy >= 363) {
        int dow = date.getDayOfWeek().ordinal();
        doy = doy - 363 - (date.isLeapYear() ? 1 : 0);
        if (doy - dow >= 0) {
          year++;
        }
      }
      return year;
    }
  }

  //-----------------------------------------------------------------------

  /**
   * Implementation of the unit.
   */
  private static enum Unit implements TemporalUnit {

    /**
     * Unit that represents the concept of a week-based-year.
     */
    WEEK_BASED_YEARS("WeekBasedYears", Duration.ofSeconds(31556952L)),
    /**
     * Unit that represents the concept of a quarter-year.
     */
    QUARTER_YEARS("QuarterYears", Duration.ofSeconds(31556952L / 4));

    private final String name;
    private final Duration duration;

    private Unit(String name, Duration estimatedDuration) {
      this.name = name;
      this.duration = estimatedDuration;
    }

    @Override
    public Duration getDuration() {
      return duration;
    }

    @Override
    public boolean isDurationEstimated() {
      return true;
    }

    @Override
    public boolean isDateBased() {
      return true;
    }

    @Override
    public boolean isTimeBased() {
      return false;
    }

    @Override
    public boolean isSupportedBy(Temporal temporal) {
      return temporal.isSupported(EPOCH_DAY);
    }

    @SuppressWarnings("unchecked")
    @Override
    public <R extends Temporal> R addTo(R temporal, long amount) {
      switch (this) {
        case WEEK_BASED_YEARS:
          return (R) temporal.with(WEEK_BASED_YEAR,
              Math.addExact(temporal.get(WEEK_BASED_YEAR), amount));
        case QUARTER_YEARS:
          // no overflow (256 is multiple of 4)
          return (R) temporal.plus(amount / 256, YEARS)
              .plus((amount % 256) * 3, MONTHS);
        default:
          throw new IllegalStateException("Unreachable");
      }
    }

    @Override
    public long between(Temporal temporal1Inclusive, Temporal temporal2Exclusive) {
      if (temporal1Inclusive.getClass() != temporal2Exclusive.getClass()) {
        return temporal1Inclusive.until(temporal2Exclusive, this);
      }
      switch (this) {
        case WEEK_BASED_YEARS:
          return Math.subtractExact(temporal2Exclusive.getLong(WEEK_BASED_YEAR),
              temporal1Inclusive.getLong(WEEK_BASED_YEAR));
        case QUARTER_YEARS:
          return temporal1Inclusive.until(temporal2Exclusive, MONTHS) / 3;
        default:
          throw new IllegalStateException("Unreachable");
      }
    }

    @Override
    public String toString() {
      return name;
    }
  }
}
